Propellant



United States PROPELLANT Raymond S. Holmes, Hamden, Conn., and Byron C. Baldridge, East Alton, and John J. ONeill, Jr., Alton, Ill., and Charles Earnest Silk, Stamford, Conn., assignors to Olin Mathieson Chemical Corporation, a corporation of Virginia No Drawing. Application May 10, 1956, 7 Serial No. 583,900

28 Claims. (Cl. 52-13) This invention relates generally to explosives and more particularly to a propellant.

This application is a continuation application of our copending applications Serial No. 360,593 and Serial No. 360,594, filed June 9, 1953.

Propellent grains having various shapes and chemical composition hav been proposed, heretofore, for caliber .30 and larger caliber cartridges but none of them have been found entirely suitable in practice. Of these various types of propellants, tubular propellent grains having dinitrotoluene coating on the grain have the least number of disadvantages and, consequently, grains of this type have been utilized almost exclusively in such cartridges. These grains are eminently suitable for the purpose except for the fact that the accuracy and efiiciency of the projectile is no longer acceptable after a relatively small number of cartridges have been fired in a machine gun or other rapid firing guns. This decrease in accuracy has been found to be due to the inner wall of the barrel substantially adjacent the breech being eroded or otherwise damaged by the gases developed by the explosion of the propellant. Heretofore, the only remedy for this condition has been to cease firing and change the gun barrel, which is of disadvantage to the operator and has not alleviated the disadvantage of short barrel life.

It is therefore an object of this invention to provide a novel propellent charge for rapid-firing guns. Another object of the invention is to provide a propellant which has improved ballistic properties in guns of caliber .30 or larger caliber. Still another object of the invention is to provide apropellant for caliber. .30 and larger sized cartridges having improved barrel erosion characteristics. A further object is to provide a method for making propellant suitable for utilization in machine guns and other rapid-fire guns of caliber .30 and larger calibers.

The foregoing objects as well as others which will become apparent from th following description are accomplished, generally stated, by providing propellent powder grains whose surface area and web are coordinated with the chemical composition thereof in such a way that cartridges loaded therewith have improved gun barrel erosion characteristics. More specifically, this invention contemplates cartridges of caliber .30 and larger calibers having a propellent charge composed essentially of propell'ent grains having a surface area within the range of from about 10 square centimeters per gram thereof to about 84 square centimeters per gram thereof, having a web between about 0.015 inch and about 0.070 inch and having a deterrent localized near the surface of the grain in the region extending from each surface not more than about-one-sixth of the web. Not less than about 3 "alieatof explosion of as low as about -l000 to about 2500 are preferred, although as stated hereinbefore, deterrents having aheat'of explosion of as high as 200 calories per gram can be utilized. Ordinarily not more than about 15 percent of the preferred class of deterrents will be required for most propellants for cartridges larger than caliber .30.

Caliber .30 propellent charges must have a surface area within the range of from about square centimeters to about 84 square centimeters per gram thereof. Not less than about 3 percent based on the weight of the propellent grain of deterrent and ordinarily not more than about 12 percent deterrent having a heat of explosion constant of less than -200 calories per gram are required for caliber .30 propellant charges. The web of the caliber .30 propellent grains must be within the range of from about 0.015 inch to about 0.025 inch and the deterrent must be dispersed in that region of the grain not more than about one-sixth of the web of the grain. Propellants for calibers larger than caliber .30 have a web of from about 0.015 of an inch to about 0.07 of an inch and a surface area of from about 10 square centimeters to about 74 square centimeters.

The propellent grains may be shaped by extruding partially or completely colloided nitrocellulose through a die and cutting the resulting rod to the required length to provide charges having a surface area of from about 10 square centimeters to about 84 square centimeters per gram. Propellent grains for calibers larger than caliber .30 having a surface area of from about 10 square centimeters to about '74 square centimeters may be formed into a globular shape by any suitable process such as, for example, the process disclosed by Schaefer in U. S. Patent 2,160,626 or may be formed by any other suitable process. The extruded powder grains may or may not have one or more perforations therein provided the specific surface is within the specified range and the deterrent is localized as specified hereinbefore.

The process disclosed by McBride in U. S. 1,955,927 has been found to be particularly advantageous for properly locating the deterrent in the grain. However, merely properly locating the deterrent in the grain when it is applied thereto is not sufficient. A deterrent must be utilized which will remain confined within that region of the propellent grain to which it is applied when the propellant is exposed to any storage or weather condition under which the other components of a cartridge are stable. Any non-migratory deterrent having a heat of explosion constant of less than 200 calories per gram can be utilized such as dialkyl phthalates like dibutyl phthalate and diamyl phthalate; diaryl phthalates such as diphenylphthalate; triphenyl phosphate, butyl stearate, diaryl dialkylureas such as diethyl diphenyl urea, methylethyl diphenyl urea and dimethyl diphenyl urea; butyl ricinoleate, glycerol sebacate, tricresyl phosphate and the like.

Web is used herein and in the appended claims in its usual sense. For instance, the Web is the minimum thickness between parallel surfaces insofar as solid or perforated grains are concerned; web is the diameter of a sphere; or Web is the minimum distance through the center of an ellipsoidal or similar shaped grain such as, for example, the type of grain usually obtained when spherical grains are compressed between rolls. Hence, the Web of a tubular grain may be the minimum dis tance between th wall bounding a perforation and another surface of the grain or it may be the distance between two external surfaces of the grain depending upon which distance is the smaller and the word Web is used herein in its usual sense in th art.

The heat of explosion constant of the constituents of powder grains is a well-known term in the industry and has been determined from the heat of combustion of the material utilizing calculations involving the formulae published by de Pauw in articles in Zeitschrift fur das gesamte Schiessund Sprengstoflwesen volume 32, pp..11, 36 and 60 (1937). Actually, the value assigned as the heat of explosion of deterrents is a constant which represents the effect of the material on the heat given off upon firing of the explosive constituents of the grain.

This constant can also be determined experimentally. In such a method, a dried sample of a propellent powder not having any deterrent in its composition is burned in an adiabatic calorimeter bomb having a nitrogen at1nosphere therein and the heat of combustion is measured by conventional procedures. Another dried sample of propellant substantially identical with the one utilized in the foregoing with the exception that a known amount of deterrent is incorporated in the grain is then burned in the bomb and the heat of combustion determined. The difference between the heat of combustion of the untreated propellant and the treated propellant divided by the weight of the deterrent is designated the heat of explosion of the deterrent. Thus the heat of explosion constant of a deterrent is a measurement of the effect of the deterrent on the explosion temperature of a propellent base material. For example, to determine the heat of explosion of dibutylphthalate a dried sample of a propellant composed essentially of about 90 percent nitrocellulose and about percent nitroglycerine was burned in a calorimeter bomb having a nitrogen atmosphere. Then another sample of this propellanttreated in accordance with this invention to contain about 7 percent dibutylphthalate was burned under similar conditions. The heat of explosion of the propellant without deterrent was found to be 1070 calories per gram of propellant burned, while the heat of explosion of the propellant including the deterrent was found to be 840 calories per gram of propellant burned. Inasmuch as 93 percent of the grain was nitrocellulose and nitroglycerine base material the heat due to the burning of this portion of the charge of propellant having a deterrent should have been (93Xl070) or 994 calories. Subtracting 840 calories which was actually obtained in the test from 994 calories leaves 154 calories difference per gram between the heat of explosion between the two propellants. This decrease is due to the deterrent since it was the only variable. There was only .07 gram of dibutylphthalate per gram of propellant so 154 must be divided by .07 to determine the effect of the deterrent on propellants in terms of grams of deterrent. In other words each gram of dibutylphthalate will reduce the heat of explosion of a propellant about 2200 calories. In order to indicate that it reduces the heat of explosion of the propellant, the number is referred to as a negative number. Hence the heat of explosion of dibutylphthalate is about 2200 calories per gram.

In accordance with the well known methods for utilizing deterrents and energizers or energizing modifiers to obtain the desired ballistic effects with nitrocellulose pro pellants, the deterrent may be adjusted within the range of from 3 percent to about percent to obtain the ballistics essential for the particular caliber and, if necessary or if desired to produce particular ballistic effects, an energizer, such as nitroglycerine, may also be incorporated in the propellent grain. Usually, from about 10 to about percent of a liquid nitric ester of a polyhydric alcohol such as, for example, nitroglycerine or nitroglycol is sufficient energizer for most double base powders.

The propellent grains of this invention have approximately twice the surface area of conventional perforated grains heretofore utilized. For example, heretofore, propellent grains containing clinitrotoluene having a surface area of about 29 square centimeters per gram of propellent and a web of about 0.021 inch have been utilized in caliber .50 cartridges. The surface area of embodiments of this invention suitable for caliber .50, on the other hand,

is within the range of about 55 to about 72 square centimeters per gram thereof, the web is about 0.016 inch to about 0.023 inch and the grain contains about 6 to about 10 percent non-migratory deterrent having a negative heat of explosion of less than about 200 localized in the region extending inwardly about one-sixth of the web from each surface of the grain. The heretofore conventional propellent grains containing dinitrotoluene utilized in caliber .60 have a web of about 0.028 inch and a surface area of about 23 square centimeters per gram while embodiments of this invention suitable for caliber .60 have a web of about 0.022 inch to about 0.028 inch, a surface area of about 45 square centimeters to about 60 square centimeters per gram thereof, and contain in the specified region of the grain from about 6 to about 10 percent by weight of one of the deterrents of the class described hereinbefore. The commercially available 20 millimeter propellant has had a surface area of about 25 square centimeters per gram and a web of about 0.027 inch while embodiments of this invention having a surface area from about 35 to about 55 square centimeters per gram, a web of from about 0.025 to about 0.032 inch and containing in the specified region of the grain from about 6 to about 10 percent of one of the class of deterrents of this invention are best suited for 20 millimeter cartridges. Heretofore, millimeter propellants have had a web of about 0.034 and a surface area of about 16 square centimeters per gram thereof while a preferred embodiment of this invention suitable for 90 millimeter has a surface area of about 32 square centimeters per gram thereof and has a web of about 0.034 inch and has about 9 percent of one of the class of deterrents confined within that-region of the grain extending inwardly from each surface about one-sixth of the web of the grain.

In carrying out this invention, the nitrocellulose powder base after the grain formation should have a specific gravity of not less than about 1.5 inasmuch as lower specific gravities are occasioned by the presence of deleterious voids which do not permit the attainment of desired ballistic properties. When a double base powder is made in accordance with this invention, the smokeless powder base should similarly be made such that it would have a specific gravity of about 1.5 or greater. The addition of the energizing modifier, such as nitroglycerine or the like, or compressing will, of course, effect an increase in the specific gravity of the powder grain to a certain extent but is not generally effective to overcome deficiency in ballistic properties resulting from an original specific gravity of less than 1.5. By non-porous grains is meant, therefore, grains which in the absence of energizing modifiers or the use of deforming pressures have a specific gravity of about 1.5 or more.

The exact reason why cartridges loaded with the propellant of this invention are less erosive to the wall and rifling of the bore of the gun barrel than are similar cartridges loaded with other propellants has not been positively resolved. However, the results obtained in actual tests under similar conditions and with similar guns and similar cartridges except for the propellant charge therein have indicated a phenomenal improvement in gun barrel life with the propellant of this invention. For example, with the propellant of this invention the barrel life has been found in one instance with a caliber .50 gun to be as much as 30 times longer than the life of a barrel of a similar gun in which cartridges were fired having heretofore available propellants made in accordance with the process disclosed in Technical Manual No. 92900 entitled Military Explosives published August 29, 1940 by the War Department of the United States Government. Thus the propellant of this invention greatly extends the life of gun barrels. For the purpose of this test, the barrel is considered no longer suitable when the flight of the projectile indicates a yaw of at least ten degrees or when the muzzle velocity of the projectile has decreased more than 200 feet per second.

about one week.

In order to further clarify the invention, the following is a detail description of an embodiment thereof:

About'100 parts by weight of nitrocellulose having a nitrogen content of about 13.2 percent are suspended in about 800 parts water. About 330 parts ethyl acetate containing about one part diphenylamine are added to the suspension and the slurry is agitated at about 70 C. until the nitrocellulose has dissolved in the ethyl acetate. About 8 parts gum arabic which has been dispersed in about 50 parts Water are added to the slurry and about one-half hour later about 33 parts sodium sulfate dissolved in about 100 parts Water are added. Agitation is continued for about 4 hours after which time the solvent is removed from the globules by gradually raising the temperature of the slurry to about 99 C. After cooling, the hardened globular powder grains are separated from the liquid phase.

Those grains passing through a screen having 0.034 inch diameter openings and remaining on a screen having 0.025 inch diameter openings are segregated from the other sized grains and about 100 parts thereof are suspended in about 330 parts Water. About 22 parts of an emulsion of about 11 parts nitroglycerine, about 4 parts ethyl acetate and about 7 parts water are added and the temperature of the slurry is raised to about 65 C. and further increased to about 70 C. in a period of about four hours. The ethyl acetate and toluene are then removed by passing air through the slurry while continuing the agitation thereof. About 13 hours are required for substantially complete removal of the solvent after which the temperature is raised to about 72 C. and about 1% parts gum arabic are added.

An emulsion of about 9 parts dibutylphthalate and about 0.05 part emulsifying agent such as gum arabic in about 20 parts water is added and the resulting slurry agitated for about hours after which the propellant grains are separated from the liquid. The water wet spheres are compressed between rolls at suificient pressure to give a web of about .019 inch after which they are air dried. About 1000 parts of the resulting grains are coated with about 5.0 parts potassium nitrate, about 2.5 parts diphenylphthalate and about one-half part dinitrotoluene by tumbling the grains therewith in a sweetie barrel for about 30 minutes at 55 C, after which about 04 part graphite is added and tumbling is continued for an additional 30 minutes. The powder is then screened and the grains'passing through a screen having openings of about 0.055 inch diameter and remaining on a screen having 0.0169 inch diameter openings are segregated for use in caliber .50 cartridges.

In another embodiment of the invention nitrocellulose having an average nitrogen content of about 13.2 percent is obtained by mixing about 3 parts nitrocellulose having a nitrogen content of about 13.4 percent with about one part nitrocellulosehaving a nitrogen content of about 12.6 percent to form a suitable powderbase, About 100 parts by Weight of the resulting powder base is dehydrated with about 125 parts of ethyl alcohol in a conventional dehydration press. The resulting block of about 100 parts nitrocellulose and about 33 parts alcohol isbroken up and 66 parts diethyl ether is added thereto to partially colloid the mass. During the agitation to completely mix the solvent with the nitrocellulose, about'one part diphenylamine is added. The colloid is next pressed into a block, forced through an extrusion die and again blocked in conventional equipment and finally grained by extruding through a die adapted to produce a solid rod, the die having an internal diameter of about 0.105 inch. The grains are next cut to a length substantially equal to their diameter. The resulting grain is not perforated. The ether-alcohol and other volatiles 'are removed by air-drying in trays stored in a room having an average temperature of about 30 C. the first 24 hours, about 40C. the next 24 hours and about 45 C. for

The resulting propellant grains are impregnated with about 10 percent nitroglycerine and are thereafter coated with about 9 percent diethyl diphenyl urea by methods similar to those described in conjunction with the foregoing caliber .50 embodiment. The grains are also treated in a sweetie barrel with potassium nitrate, dinitrotoluene and graphite in accordance with the method described for caliber .50 but screening is ordinarily not required when the grains have been shaped by an extrusion process. The resulting grains are a preferred embodiment for use in millimeter cartridges.

A powder base having an average nitrogen content of about 13.2 percent is obtained by mixing about 3 parts by weight nitrocellulose having a nitrogen content of about 13.4 percent with about one part nitrocellulose having a nitrogen content of about 12.6 percent, About parts by weight of the resulting nitrocellulose is dehydrated with about parts of ethyl alcohol in 'a conventional dehydrating press. The resulting block .of about 100 parts nitrocellulose and about 33 parts alcohol is broken up and 66 parts diethyl ether is added thereto to partially colloid the mass. During the agitation to completely mix the solvent with the nitrocellulose, about one part diphenylamine is added. The colloid is next pressed in to a block, forced through an extrusion die and again blocked in conventional equipment and finally grained by extruding through a die adapted to produce a solid rod, the die having an internal diameter of about 0.042 inch. The solid rod is cut to lengths substantially equal to its diameter to form propellent grains. The ether-alcohol and other volatiles are removed by air drying in trays stored in a room having an average temperature of about 30 C. the first 24 hours, about 40 C. the next 24 hours and about 45 C. for about one week.

About 100 parts of the resulting propellent grains'are suspended in about 330 parts water. About 22 parts of an emulsion of about 11 parts nitroglycerine, about 4 parts ethyl acetate and about 7 parts toluene and about 0.1 part gum arabic in about 75 parts water are added and the temperature of the slurry is raised to about 65 C. and further increased to about 70 C. in a period of about four hours. The ethyl acetate and toluene are then removed by passing air through the slurry while continuing the agitation thereof. About 13 hours are required for substantially complete removal of the solvent after which the temperature is raised to about 72 C. and about 1% parts gum arabic are added.

An emulsion of about 72 parts dibutylphthalate and about 0.05 part emulsifying agent such as gum arabic in about 20 parts water is added and the resulting slurry agitated for about 5 hours after Which the propellent grains are separated from the liquid. About 1000 parts of the resulting grains are coated with about 5.0 parts potassium nitrate, about 2.5 parts diphenylphthalate and about one-half part dinitrotoluene by tumbling the grains therewith in a sweetie barrel for about 30 minutes at 55 C. after which about 0.4 parts graphite are added and tumbling is continued for an additional 30 minutes. The resulting grains have a surface area of about 77 square centimeters per gram of propellant, have a web of about 0.016 inch and contain about 6.5 percent by weight of dibutylphthalate dispersed in that region of the grain extending from each surface thereof about 0.003 inch. While the immediately foregoing embodiment has been described in detail with respect to caliber .30 propellants, propellent charges for other guns in this range of calibers such as caliber .303, 7.92 millimeter, 7 millimeter and the similar calibers are contemplated by the invention.

While the foregoing embodiments have been described in'detail some deviations can be made from the various processing steps without deleteriously affecting the properties of the powder grains. For example, any other process which is capable of applying the deterrent to the surface of the powder grains and which will insure that the deterrent'will penetrate the surface of the grain but will not migrate into the core of the grain can be utilized. Variations can be made in the process of forming the propellent grains provided that the resulting grains have a composition and a geometry such that they will fall within the critical limits presented hereinbefore for the surface area and web. Any process capable of substantially uniformly dispersing the nitroglycerine or other energizing modifier throughout the grains can be utilized and other known modifiers such as, for example, carbon black can be incorporated in the powder grains. Even other variations Will become apparent to those skilled in 'the art and the invention is not to be limited by any of the details. herein set forth but is limited only by the scope of the appended claims.

Having thus described the invention, what is claimed and desired to secure by Letters Patent is:

1. A propellant having improved ballistic characteristics composed essentially of substantially non-porous extruded nitrocellulose base propellent grains having a surface area of from about 10 square centimeters per gram to about 84 square centimeters per gram thereof, a web of from about 0.015 inch to about 0.07 inch, and having within the region of the grain which extends from each surface thereof not more than about one-sixth of the web of the propellent grain not less than about 3 percent of a deterrent having a heat of explosion constant of less than about 200 calories per gram.

2. A propellent charge composed essentially of extruded nitrocellulose powder base propellent grains whose cut surfaces are so spaced that the surface area of the' grains is from about 75 to about 84 square centimeters -per gram thereof, the web is from about 0.015 to .about 0.025 inch, and having dispersed throughout the region of the grain which extends from each surface about one-sixth ofthe web of the grain at least about 3 percent of a deterrent having a heat of explosion of less than about 200 calories per gram.

3. A propellent charge composed essentially of extruded-nitrocellulose powder base propellent grains having a surface area of about 77 square centimeters per gram thereof, a web of about 0.016 inch and having dispersed throughout the region of the grain which extends from each surface thereof about one-sixth of the web of the grain at least about 3 percent of a deterrent having "a Lheatof explosion of less than about 200 calories per gram. I q

'4. A propellent charge composed essentially of extruded nitrocellulose powder base propellent grains hav- 'ing a surface area of about 77 square centimeters per gram thereof, a web of about 0.016 inch and having dispersed throughout the region of the grain which extends from each surface about one-sixth of the Webof the grain about 6.5;percent of a non-migratory deterrent having a heat of explosion of less than about 200 calories per gram.

5. A propellent charge composed essentially of solid substantially cylindrical nitrocellulose powder base propellent grains having a surface area of from about '75 to about 84 square centimeters per gram thereof and a web of from about 0.015 to about 0.025 inch, and having dispersed throughout the region of the grain which extends from each surface about one-sixth of the Web of the grain at least about 3% of a substantially non-migratory deterrent having a heat of explosion of less than about 200 calories per gram. I A

6. A propellent charge composed essentially of extruded nitrocellulose powder base propellentgrains impregnated 'with about 10 percent of a liquid explosive nitric ester of a polyhydric alcohol and having a surface area of about 75 to about 84 squarecentimeters, a web of from about 0.015 inch to about 0.025 inch and having dispersed throughout the region of the grain extending from each surface about one-sixth of the web of the grain at least about 3 percent of a non-migratory deterrent having a heat of explosion of less than about 200 calories per gram. Y I

7."A propellent charge composed essentially of extruded nitrocellulose powder base propellent grains having a surface area of from about 75 to about 84 square centimeters per gram thereof, a web of from about 0.015 inch to about 0.025 inch, and having dispersed throughout the region of the gra-inwhich extends from each surface about one-sixth of the web at least 3% of a nonmi-gratory deterrent having a heat of explosion of less than about l000 calories per gram.

8. A propellant having improved ballistic characteristics composed essentially of substantially non-porous nitrocellulose base propellent grains having a surface area of from about -10 square centimeters per gram to about 74 square centimeters per gram thereof, a web of from about 0.015 inch to about 0.07 inch, and having dispersed throughout the region of the grains extending from each surface thereof not more than about one-sixth of the web of the propellent grainfrom about 3% to about 15% of a deterrent having a heat of explosion constant of less than about -200 calories per gram.

9. A propellant having improved ballistic characteristio's composed essentially of substantially non-porous nitrocellulose base propellent grains having a surface area of from about 10 square centimeters per gram to about 74 square centimeters per gram thereof, a web of from about 0.015 inch to about 0.07 inch, and having dispersed throughout the region of the powder grain which extends from the surfaces thereof not more than about one-sixth of the web of the propellent grain, not less than about 3 percent of a deterrent having a heat of explosion constant of less than about 200 calories per gram.

'1-0. A propellent charge for calibers larger than caliber .30 having improved ballistic characteristics, said charge being composed essentially of nitrocellulose base propellent g'rains having a surface area of from about 10 square centimeters to about 74 square centimeters per gram thereof, a web of from about 0.015 inch to about 0.07

pellent grains containing about 10 percent nitroglycerine and having a surface area of from about 10 square centimeters to about 74 square centimeters per gram thereof, a web of from about 0.015 inch to about 0.07 inch and having substantially uniformly dispersed throughoutthe region of the grains which extends from the "surface thereof not more than about one-sixth of the'web of the propellent grain not less than about 3% :Of a deterrent having a heat'of explosion constant of less than about 200 calories per gram.

12. A propellant having improved ballistic characteristics in caliber I50 guns composed essentially of substantially hon-porous nitrocellulose base grains containing about l'Opercent nitroglycerine and having a surface area of from about 55 square centimeters per gram to about 72 square centimeters per gram thereof, a web of from about 0.016 inch to about 0.023 inch and having dispersed only in the region-of the grains extending from each surface thereof from about 6 percent to about 10 percent deterrenthaving a heat of explosion constant ofless'than about 200 calories per gram of propellant.

13. A propellant having improved ballistic characteristics in caliber guns composed essentially of substantially-non porous' nitrocellulose base grains containing nitroglycerine and having a surface area of from about 45 square centimeters per gram to about 60 square centimeters per gra'm thereof, a web offrom about- 0.022

inch and about 0.028 inch and having dispersed only'in the .region of the grains extending .from each surface thereof from about 6 percent to about percent deterrenthaving a heat of explosion constant of less thanabout 200 calories per gram of propellant.

14. ,A propellant having improved ballistic characteristics in 20 millimeter guns composed essentially of substantially non-porous nitrocellulose base grains containingabout 10 percent nitroglycerineand having a surfacearea of from about 35 square centimeters per. gram to about 55 square centimeters per gram thereof, a web of from about 0.025 inch to about 0.032 inch and having dispersed only .in the region of the grains extending inwardly from each surface thereof from about .6 to about 10 percent deterrent having a heat of explosion constant of less than about 200 calories per gram of propellant.

15. A propellant having improved ballistic characteristicsin .90 millimeter guns composed essentially of substantially non-porous nitrocellulose base grains containing about 10 percent nitroglycerine having a surface area of about 32 square centimeters per gram thereof, a web of about 0.034 inch and havingdispersed only in the region of the grains extending inwardly from each surface thereof about 9 percent deterrent having a .heat of-explosion constant of less than about 200 calories per gram of propellant.

16. In a method for making propellants, theprocess which comprises colloiding nitrocellulose, extruding the resulting powder base through a die,subdividing the resulting rod of powder base into propellant grains having dimensions providing a surface area of from about 10 to about 84 square centimeters per gram and a web of about 0.015 inch to about 0.07 inch, coating the powder grains with a deterrent having a heat of explosion constant of less than about 200 calories per gram, and heating the coated grains until at least about 3 percent deterrent penetrates only the region of the grain which extends from the surface thereof about one-sixth of the web of the grain.

17. In a method for making propellants, the process which comprises colloiding nitrocellulose, extruding the resulting powder base through a die, subdividing the resulting rod of powder base into propellent grains having dimensions providing a surface area of about 75 to about 84 square centimeters per gram and a web of about 0.015 to about 0.025 inch, coating the grains with a non-migratory deterrent having a heat of explosion constant of less than about 200 calories per gram, and heating the coated grains until not less than about 3 percent deterrent penetrates only the region of the grain which extends from each surface thereof about one-sixth of the Web of the grain.

18. In a method for making propellants, the process which comprises colloiding nitrocellulose, extruding the resulting powder base through a die, subdividing the resulting rod into propellent grains having dimensions providing a surface area of from about 10 to about 84 square centimeters per gram and a web of from about 0.015 to about 0.07 inch, coating the resulting grains with a liquid explosive nitric ester, heating the grains until said ester penetrates and becomes substantially uniformly dispersed throughout the grain, coating the grains with a nonmigratory deterrent having a heat of explosion constant of less than about 200 calories per gram, and heating the grains until at least 3 percent deterrent penetrates only the region of the grain which extends from each surface thereof about one-sixth of the web of the grain.

19. In a method for making propellants, the process which comprises colloiding nitrocellulose, extruding the resulting powder base through a die, subdividing the rod into propellent grains having dimensions providing a surface area of about 75 to about 84 square centimeters per gram and a web of about 0.015 to about 0.025 inch, coating the resulting grains with a liquid explosive nitric ester, heating the grains until said ester penetrates the grain and is substantially uniformly dispersed therein, coating 10 the grains .with a non-migratory deterrent havinga heat of explosion constant of less than 200 calories per gram thereof, and heatingthecoated grains until at least about 3 percent deterrent penetratesonly the region of the grain which extendsfrom each surface thereof about one-sixth of the web of the grain.

20. In a method for making propellants, the process which comprises colloiding nitrocellulose, extruding the resulting powder base through a die, cutting 'the resulting rod of powder base into lengths, rolling said lengths into powder grains havingdimensions providing a surface area of from about 75 to about 84 square centimeters per gram and a web of from about 0.015 to about 0.025 inch, coating the grains with a deterrent having a heat of explosion constant of less than about 200 calories per gram thereof, and heating the coated grains until at least-about3 percent of the deterrent-penetrates only that region of the grain which extends from the surface thereof about onesixth of the Web.

21. In a method for making propellants having improved ballistic characteristics, the process -which comprises subdividinga nitrocellulose powder base into substantially non-porous grains having dimensions providing a surface area of from about 10 to about 74 square centimeters per gram thereof and .a web of from about 0.015 inch to about 0.07 inch, coating the grains with a non-migratory deterrent having a heat of explosion constant of less than about 200 calories per gram, and thereafter heating the coated grains until from about 3 percent to about 15 percent deterrent penetrates only the region of the grain which extends from the surface thereof about one-sixth of the web of the grain.

22. In a method for making propellants having improved ballistic characteristics, the steps which comprise subdividing the nitrocellulose powder base into nonporous grains having dimensions providing a surface area of about 10 to about 74 square centimeters per gram thereof and a web of from about 0.015 inch to about 0.07 inch, coating the grains with a non-migratory deterrent having a heat of explosion constant of less than about 200 calories per gram, and thereafter heating the coated grains until not less than 3 percent deterrent penetrates only the region of the grains which extends from each surface thereof about one-sixth of the web of the grains.

23. The process for making propellants having improved ballistic characteristics which comprises subdividing a nitrocellulose powder base into non-porous grains having dimensions providing a surface area of about 10 to about 74 square centimeters per gram thereof and a web of from about 0.015 inch to about 0.07 inch, coating the grains with a liquid explosive nitric ester of a polyhydric alcohol, heating the grains until said ester is dispersed substantially uniformly therein, coating the grains with a non-migratory deterrent having a heat of explosion constant of less than about 200 calories per grams, and thereafter heating the coated grains until not less than about 3 percent deterrent penetrates only the region of the grain which extends from each surface thereof about one-sixth of the web of the grains.

24. The process for making propellants for caliber .50 guns which comprises subdividing a nitrocellulose powder base into non-porous grains having dimensions providing a surface area of from about 55 to about 72 square centimeters per gram thereof and a web of from about 0.016 inch to about 0.023 inch, coating the grains with a liquid explosive nitric ester of a polyhydric alcohol and heating the grains until from about 10 to about 20 percent of said ester is substantially uniformly dispersed therein, coating the grains with a non-migratory deterrent having a heat of explosion constant of less than -200 calories per gram, and thereafter heating the grains until from about 6 to about 10 percent deterrent penetrates only the region of the grains extending from each surface thereof about one-sixth of the web of the grains.

25. The process for making propellants for caliber .60 guns which comprises subdividing a nitrocellulose powder base into non-porous grains having dimensions providing a surface area of from about 45 to about 60 square centimeters'per gram thereof and a web of from about 0.022 inch to about 0.028 inch, coating the grains with a liquid explosive nitric ester of a polyhydric alcohol, heating the coated grains until from about 10 to about 20 per cent of said ester is dispersed substantially uniformly therein, coating the grains with a nn-rnigra tory deterrent having a heat of explosion constant of less than about -200 calories per gram, and thereafter heating the coated grains until about 6 to about l0'percent deterrent penetrates only the region of the grains extending from each surface thereof about one-sixth of the web of the grain.

26. The process for making propellants for 20 millimeter guns which comprises subdividing a nitrocellulose powder base into non-porous grains having dimensions providing a surface area of from about 35 to about 55 square centimeters per gram thereof and a web of from about 0.025 inch to about 0.032 inch, thereafter coating the grains with a liquid explosive nitric ester of a polyhydric alcohol, heating the grains until from about 10 to about 20 percent of said ester is substantially uniforrnly dispersed therein, coating the grains with a nonmigratory deterrent having a heat of explosion constant of less than about -200 calories per gram, and thereafter heating the coated grains until from about 6 to about 10 percent deterrent penetrates only the region of the grains extending from each surface thereof about one-sixth of the web of the grains.

27. In a method for making propellants, the process which comprises colloiding nitrocellulose, extruding the resulting powder base through a die, cutting the extruded rod into lengths, rolling said lengths into powder grains having dimensions providing a surface area of from about 10 square centimeters per gram to about 74 square centimeters per gram and a web of from about 0.015 inch to about 0.07 inch, coating the grains with a deterrent having a heat of explosion constant of less than about -200 calories per gram thereof, and thereafter heating the coated grains until at least 3 percent deterrent penetrates the outer one-sixth of the web of the grain.

28. A propellant having improved ballistic characteristics composed essentially of substantially non-porous extruded nitrocellulose base propellent grains impregnated'with a liquid explosive nitric ester of a polyhydric alcohol having a surface area of from about 10 square centimeters per gram to about 84 square centimeters per gram thereof, a web of from about 0.015 inch to about 0.07 inch, and having within the region of the grain which extends from each surface thereof not more than about one-sixth of the web of the propellent grain not less than about 3 percent of a deterrent having a heat of explosion constant of less than about 200 calories per gram.

No references cited. 

